Human apyrase represents a highly promising therapy for acute ischemic stroke which is a leading cause of death and disability with almost no effective therapy for most patients. Using a protein informatics approach, we have successfully engineered a human apyrase which exhibits significantly higher enzymatic activity and platelet inhibition than the wild-type apyrases. Importantly, the optimized apyrase conferred cerebroprotection against experimental stroke while preventing intracerebral hemorrhage. With the Phase II grant support, we will determine whether apyrase therapy is more effective while having lower bleeding risk than aspirin and a GPIIb/IIIa receptor antagonist, in combination with r-tPA for thrombolysis of stroke occlusion. PUBLIC HEALTH RELEVANCE: We will utilize clinically relevant embolic stroke models in rats to validate whether human apyrase improves efficacy and reduce cerebral hemorrhage associated with thrombolytic treatment of ischemic stroke.